COS Naming Service Provider for JNDI

Contents

  1. Introduction
  2. Conformance
  3. Environment Properties
  4. ORB Initialization
  5. Root Naming Context Initialization
  6. Names and URLs
  7. API Mapping
  8. Converting CORBA Programs to use JNDI
  9. Security Considerations

Introduction

The Common Object Services Name Server serves up CORBA object references using the COS Naming package.

The JNDI/COS naming service provider implements the javax.naming.Context interface on top of the COS Naming package in order to allow applications to use JNDI to access the COS Name Server. JNDI can also be used to access other naming and directory services, in addition to the COS Name Server, thereby offering the CORBA application one interface for accessing different naming and directory services.

This document describes the features of the COS naming service provider and contains details of how JNDI is mapped to the COS naming package.

Conformance

The COS naming service provider for JNDI uses Java IDL, the Java programming language mapping to the industry standard Object Management Group Interface Definition Language (OMG IDL). In particular, it uses the COS Naming Service.

The complete specification for COS Naming can be obtained from OMG.

The syntax of names conforms to the Interoperable Naming Service (INS) specification (99-12-03), with backward compatibility support for the previous version of INS, OMG TC Document orbos/98-10-11. This is described in Names and URLs.

Environment Properties

The following JNDI environment properties are relevant for the COS naming service provider. See the JNDI documentation for a description of how properties are initialized using the environment properties, system properties, applet parameters, and resource files.

java.naming.factory.initial

This property is used to select the COS naming service provider; it's not actually used by the provider itself. It specifies the class name of the initial context factory for the provider.

For example:

env.put(Context.INITIAL_CONTEXT_FACTORY, "com.sun.jndi.cosnaming.CNCtxFactory");

This property must be set if you are using the COS naming service as the initial context. The only exception is if you supply only URLs to the initial context, in which case, you don't need to specify this property. See Names and URLs for details.

java.naming.provider.url

This property is used to configure the root naming context and/or the Object Request Broker (ORB). Its value is the string representation of a URL.

If this property is not specified, then the ORB is initialized using the java.naming.corba.orb property, the java.naming.applet property, or other ORB initialization properties. The root naming context is obtained by invoking 

orb.resolve_initial_references("NameService");

If the URL scheme is one of "IOR", "corbaname", or "corbaloc", as specified in the INS specification (99-12-03), then the root naming context is that named by the URL. The ORB is initialized using the java.naming.corba.orb property, the java.naming.applet property, or other ORB initialization properties.

If the URL scheme is either "iiop" or "iiopname", then the host and port fields of the URL are used to initialize the ORB. An "iiopname" URL must conform to the now obsolete INS specification (98-10-11). It has the form: 

iiopname://[<addr_list>][/<cosnaming_name>]

The "iiop" URL scheme is supported for backward compatibility with an older version of the INS specification. It has the form: 

iiop://[<host>[:<port>]][/<cosnaming_name>]

For both "iiop" and "iiopname" URLs, if <host> is not specified, then it defaults to "localhost" for an application and the applet's host for an applet. If <port> is not specified, then it defaults to 9999 for "iiopname", and 900 for "iiop". The root naming context is obtained by invoking the following method on the ORB: 

orb.resolve_initial_references("NameService");

If <cosnaming_name> is nonempty, then the root naming context is the naming context named by cosnaming_name.

If the URL scheme is not one of "iiop", "iiopname", "IOR", "corbaname", or "corbaloc", then the URL must name a location that contains the stringified IOR of the root naming context. For example, if the property contains "file:/nsdir/ior", then the file /nsdir/ior must contain a stringified IOR. The URL scheme can be any for which there is a corresponding URL protocol handler ( java.net.URLStreamHandler). See the java.net.URL class for details. The stringified IOR is read from the data stream corresponding to the URL by using a character encoding of ISO Latin-1. The stringified IOR is the first line in the stream that contains the prefix "IOR:". For example, if the URL scheme is "http", then the headers in the stream are skipped and the first line that contains the prefix "IOR:" is returned as the IOR.

When the property specifies a stringified IOR or the location of one, the root naming context is that named by the the stringified IOR. The ORB is initialized using the java.naming.corba.orb property, the java.naming.applet property, or other ORB initialization properties. 

java.naming.corba.orb
This property specifies the ORB that the program is using. When the JNDI COS naming service provider needs to use an ORB, for example, to look up the "NameService" initial reference or to turn a stringified IOR into an object reference, it will use this ORB.

In an application you can set this property as follows: 

ORB orb = ORB.init(args, null);
Hashtable env = new Hashtable(5, 0.75f);
env.put("java.naming.corba.orb", orb);
...
In an applet, you can set it as follows: 
public class MyApplet extends Applet {

    public someInitMethod() {
        ORB orb = ORB.init(this, null);
        Hashtable env = new Hashtable(5, 0.75f);
        env.put("java.naming.corba.orb", orb);
        ...
    }
...
}
If this property is not set, then the java.naming.provider.url property, the java.naming.applet property, or the ORB initialization properties are used to initialize the ORB. 
java.naming.applet
This property specifies the applet that the program is using. It is used to initialize the ORB to be used by the COS naming service provider. Its parameters are used for setting JNDI-related properties; see the JNDI documentation for details. 
public class MyApplet extends Applet {

    public someInitMethod() {
        Hashtable env = new Hashtable(5, 0.75f);
        env.put("java.naming.applet", this);
        ...
    }
...
}
    
java.naming.factory.state
A colon-separated list of the fully qualified class names of state factory classes used to get an object's state for storing given the object itself. You can use this mechanism to transform an object into forms that can be stored into a COS name server. The COS name server supports storing CORBA objects.

A state factory that transforms a java.rmi.Remote into a CORBA object is supplied by default. This factory is useful for applications that use RMI-IIOP. You can supply other factories to affect the transformation of other objects into CORBA objects for storing. See javax.naming.Name, javax.naming.Context, java.util.Hashtable)"> javax.naming.spi.NamingManager.getStateToBind() for details. 

java.naming.factory.object
A colon-separated list of the fully qualified class names of object factory classes for transforming a CORBA object. You can use this mechanism to transform an object into forms expected by the application. For example, a specialized object factory could do the appropriate narrowing to return an object of the expected type. See javax.naming.Name, javax.naming.Context, java.util.Hashtable)"> javax.naming.spi.NamingManager.getObjectInstance() for details. 
java.naming.batchsize
Specifies the batch size to use in CosNaming::BindingIterator.next_n when getting the results of a list()/listBindings(). The default is "100."

For example, the following sets the batch size to be 24. 

    
env.put(Context.BATCHSIZE, "24");
ORB initialization properties
You can specify CORBA related properties such as those with the "org.omg.CORBA." prefix as properties. Properties of type String are used to initialize the ORB.

ORB Initialization

The properties that affect which ORB is used and how the ORB is initialized are:

The following algorithm is used to determine which ORB is used:

  1. If java.naming.corba.orb has been set, then its value (an ORB) is used.

  2. Otherwise, the provider will internally initialize and use an ORB as follows:

    a) Any org.omg.CORBA.* properties and properties of type String are extracted and used as part of the Properties argument to the ORB.init() method. You can use this mechanism to specify, for example, the ORB implementation or host to use.

    b) If java.naming.provider.url has been set and it contains a URL of scheme "iiop" or "iiopname", then the host and port number specified in the URL are used as part of the Properties argument to the ORB.init() method, overriding any org.omg.CORBA.ORBInitialHost and org.omg.CORBA.ORBInitialPort properties set up in (a).

    c) The Properties instance constructed in (a) and (b) are passed to ORB.init() along with the Applet instance in java.naming.applet property, or an empty String[] if java.naming.applet was not supplied.

If the properties employed in steps (a), (b) and (c) contain no relevant information for initializing the ORB, then the Java IDL implementation's defaults are used. Typically that means port 900 on the local host for an application, and port 900 on the applet host for an applet are used. Note that when the ORB is initialized using ORB.init(), its arguments are checked in the following order: (from org.omg.CORBA.ORB javadoc)

  1. Check in Applet parameter or application string array, if any
  2. Check in properties parameter, if any
  3. Check in the System properties (currently applications only)
  4. Fall back on a hardcoded default behavior (use the Java IDL implementation)

Root Naming Context Initialization

The root naming context is initialized either using the java.naming.provider.url property or by a resolve_initial_references() call on the ORB. If the java.naming.provider.url property is set but contains neither an "iiop" or "iiopname" URL, then it is assumed to contain a stringified IOR, a "corbaname" or "corbaloc" URL of an IOR, or a URL containing the location of a stringified IOR. The IOR is used to obtain the root naming context and must be that of a CORBA object of type CosNaming::NamingContext.

If the java.naming.provider.url has not been set, then the root naming context is obtained by invoking the following method on the ORB: 

        orb.resolve_initial_references("NameService");

Names and URLs

String Names

String names accepted by the java.naming.Context methods are JNDI composite names in which each component is the stringified form of a CosNaming::NameComponent.

A CosNaming::Name contains a sequence of CosNaming::NameComponent. The stringified form of a component is the concatenation of the component's id, the kind separator character ('.'), and the component's kind. The occurrence of any meta characters ('.', '/', or '\') in either the id or kind is escaped using the escape character ('\'). The stringified form of a CosNaming::Name is defined in Section 3.5 of the INS specification (99-12-03).

The JNDI composite name syntax is very similar to, but not identical to, the INS syntax. There are minor differences with respect to the treatment of escape and quote characters. If you want to use names with the precise INS syntax, then you should use the overloads that accept a Name argument instead of a String argument. The Name argument should be a value returned by nameParser.parse(), where nameParser is a value obtained from the COS naming service provider. See the Name Parsing section.

URL String Names

The URL form of a CosNaming::Name is defined in the INS specification.

corbaname:<corbaloc_obj>["#" <cosnaming_name>]
where <corbaloc_obj> is
<corbaloc_obj> = <obj_addr_list> ["/" <key_string>]
and <obj_addr_list> is a list of addresses as defined in a "corbaloc" URL and <key_string> is a key string as defined in a "corbaloc" URL. <cosnaming_name> is the stringified form of an INS name (see Name Parsing).

For backward compatibility with older versions of the INS, the following URL schemes are also supported.

iiopname://[<addr_list>][/<cosnaming_name>]

where <addr_list> specifies a list of host/port pairs. If <port> is not specified, then it defaults to 9999. <cosnaming_name> is the stringified form of an INS name.

iiop://<host>[:<port>][/<cosnaming_name>]

If <port> is not supplied, then it defaults to 900. <cosnaming_name> is the stringified form of an INS name.

When you supply an "iiop" or "iiopname" URL to the initial context in this way, the ORB supplied to the initial context is used if its string_to_object() method supports the 99-12-03 INS specification. Otherwise, the ORB is ignored and the server and port designations in the URL are used to create an ORB. The value of the java.naming.factory.initial property is ignored for the purposes of resolving the URL.

Note that this rule is not used when you supply a "corbaname" URL to the initial context. For a "corbaname" URL, the ORB supplied to the initial context is used because the ORB is needed to resolve the "corbaname" URL. Name Objects

The Name argument to a Context method is treated as a sequence of strings, each representing a stringified CosNaming::NameComponent.

Name Parsing

The COS naming service provider supports names in the syntax specified in the INS specification. In short, the syntax is that components are left-to-right slash ('/') separated and case-sensitive. The id and kind of each component are separated by the period character ('.').

Here is a code fragment that uses the name parser from the COS naming service provider to eventually do a lookup using an INS name. 

String insName = ...;
InitialContext ctx = new InitialContext(env);   // env contains init properties
NameParser parser = ctx.getNameParser("");      // parser for INS names
Name name = parser.parse(insName);              // get parsed INS name
Object obj = ctx.lookup(name);                  // do lookup

API Mapping

The COS name server supports only naming operations. The COS naming service provider maps the javax.naming.Context methods to use the appropriate COS Naming calls. 

addToEnvironment()
Records change to environment property but does not reinitialize ORB. 
bind()
Binds an object to the specified name.

If the object being bound is an org.omg.CosNaming.NamingContext, then CosNaming::NamingContext.bind_context is used. If it is an org.omg.CORBA.Object, then CosNaming::NamingContext.bind is used. The binding of any other type of object is not supported unless the object can be converted into an org.omg.CORBA.Object using the state factory mechanism described next.

Before the bind is performed on the naming server, the COS naming service provider uses javax.naming.spi.NamingManager.getStateToBind() to allow the object to be transformed into a org.omg.CORBA.Object. The getStateToBind() method uses the state factories available to the COS naming service provider. If the state factory accepts a java.rmi.Remote object, then it is responsible for obtaining the object's RMI-IIOP stub and connecting it to the ORB associated with the context. The connected stub is the object that will be bound in the naming server.

By default, the COS naming service provider supplies and uses a state factory that transforms an object implementing the java.rmi.Remote interface to an org.omg.CORBA.Object following the requirements described above. This factory uses the utilities in the javax.rmi.CORBA package. You can supply additional state factories to transform objects into CORBA objects. 

close()
Releases any internal data structures used. 
composeName()
Concatenates the supplied name to the prefix. 
createSubcontext()
Uses CosNaming::NamingContext.bind_new_context to create and bind a new context. 
destroySubcontext()
Uses CosNaming::NamingContext.destroy to destroy the named context. Then uses CosNaming::NamingContext.unbind to remove the binding. 
getEnvironment()
Returns the environment of this context. 
getNameInNamespace()
Returns the INS name of this context relative to the root of the Cos Naming namespace. 
getNameParser()
Returns a name parser for parsing INS names. 
lookup()
lookupLink()
Uses CosNaming::NamingContext.resolve to lookup the name. It returns a CORBA object reference except when the reference is that of a CosNaming::NamingContext, in which case a Context object is returned instead. NamingManager.getObjectInstance() is called before the object is returned in case the application or user has supplied object factories. 
list()
listBindings()
Uses CosNaming::NamingContext.resolve to get the object reference for the context, and then uses CosNaming::BindingIterator and helper classes to iterate through the context. The objects bound to the names are obtained by calling CosNaming::NamingContext.resolve on them. NamingManager.getObjectInstance() is called before the object is returned in case the application or user has supplied object factories. 
removeFromEnvironment()
Removes the specified property from the environment but does not otherwise update the context. 
rebind()
If the object being bound is an org.omg.CosNaming.NamingContext, then CosNaming::NamingContext.rebind_context is used. If it is an org.omg.CORBA.Object, then CosNaming::NamingContext.rebind is used. See bind() for details on the use of state factories to transform the argument into an org.omg.CORBA.Object. 
rename()
This method is implemented using bind() followed by unbind(). It is not atomic. 
unbind()
Uses CosNaming::NamingContext.unbind to unbind the object.

Converting CORBA Programs to use JNDI

This section explains how to modify your Java IDL program to use JNDI. The explanation uses the Java IDL sample programs helloClient.java and helloServer.java.

  1. Generate the stubs from the IDL file. 

    # idltojava -fclient -fserver hello.idl

    This creates the client (helloClient.java) and server (helloServer.java) skeletons, and a directory containing common code (e.g. HelloApp/*.java).

  2. Fill in the code for the client and server programs.

  3. Modify (or copy the client and server files) to use JNDI instead of COS Naming directly.

    • Replace the import to use javax.naming.*;
      Delete: 
      import org.omg.CosNaming.*;
import org.omg.CosNaming.NamingContextPackage.*;
      Add: 
      import javax.naming.*;
    • Replace how you get the initial reference to "NameService" with InitialContext, supplying the initial context the ORB being used by the current application.
      Delete: 
      org.omg.CORBA.Object objRef = 
   orb.resolve_initial_references("NameService");
NamingContext ncRef = NamingContextHelper.narrow(objRef);
      Add: 
      Hashtable env = new Hashtable(5, 0.75f);
env.put("java.naming.corba.orb", orb);
Context ic = new InitialContext(env);
    • Replace the call to resolve() to use lookup().
      Delete: 
      // resolve the Object Reference in Naming
NameComponent nc = new NameComponent("Hello", "");
NameComponent path[] = {nc};
hello helloRef = helloHelper.narrow(ncRef.resolve(path));
      Add: 
      // resolve the Object Reference using JNDI
hello helloRef = 
helloHelper.narrow((org.omg.CORBA.Object)ic.lookup("Hello"));

Security Considerations

When a security manager has been installed, grant to the application using JNDI and the COS naming service provider the following permissions: 

permission java.net.SocketPermission "host[:port]", "connect";
For each host/port identified in the java.naming.factory.initial property, in URL string names supplied to context methods, in ORB initialization parameters and properties, and in object references.